A binocular night vision device uses a pair of monocular night vision scopes which are mounted and associated with one another in such a way as to provide the user of the device with binocular vision, thereby allowing the user to have a night-time view with depth perception. Users typically operate the night vision device in a variety of positions, such as standing erect, lying flat on the ground, sitting in a cockpit of an airplane, hiding behind protective cover, and so forth. Given the wide variety of positions a user may operate a night vision device, many night vision devices include provisions for adjustably tilting (i.e., rotating) the night vision device with respect to the eye of the user to adapt the night vision device to the body orientation of the user. Furthermore, field helmet mounted optical devices may include provisions for locking the rotational position of the night vision device once the night vision device is rotated to a desired position.
In practice, night vision devices are often subject to violent external movements or environmental changes, such as temperature adjustments. For example, helmet mounted night vision devices used for aviation experience high and low frequency vibration, mechanical shock and multi-axis elevated G loads. Under those conditions, many conventional devices for retaining the night vision device in a fixed position are often inadequate for preventing the night vision device from drifting from its original setting with respect to the field helmet, thereby requiring constant readjustment of the night vision device.
In view of the foregoing, there is a continuing need to further develop and refine devices for selectively locking a helmet mounted night vision device in a fixed position, in the interests of performance, safety and convenience.